Stents are used in medical practice to provide support to various lumens in the human body. One of the most common uses is in conjunction with percutaneous transluminal coronary angioplasty (PTCA), which is used to treat stenosis, a narrowing of a blood vessel, leading to restricted blood flow. In PCTA, a balloon inserted into the narrowed section of the artery ‘squashes’ the cholesterol plaques (atherosclerosis) against the artery walls, thus widening the size of the lumen and increasing blood flow. A stent is often used in conjunction with angioplasty to hold open an artery, allowing for unrestricted blood flow, or to support a weakness in the artery wall called an aneurysm. The artery can react to the stent, perceive it as a foreign body and respond by mounting an immune system response which leads to renewed narrowing near to or inside the stent. Such a reoccurrence of stenosis is known as Restenosis.
Furthermore, the action of the angioplasty itself can cause damage to the artery walls, and it responds by using physiological mechanisms to repair the damage. Damage to the blood vessel wall by angioplasty triggers physiological response that can be divided into two stages. The first stage, which may occur immediately after tissue trauma, is thrombosis. A blood clot may form at the site of the damage and further hinder blood flow. This is accompanied by an inflammatory immune response. The second stage may occur 3-6 months after surgery and is the result of proliferation of cells in the intima, a smooth muscle wall in the vessel. This is known as Neointimal hyperplasia (NIHA), and may occur in 20-30% of patients treated with bare metal stents.
Drug-eluting stents are stents coated with pharmaceuticals that inhibit tissue growth. By controlled release of the drugs onto the endothelial surface, the restenosis process may be controlled or inhibited, thus reducing the risk of restenosis from scar-tissue and cell proliferation. With such drug-eluting stents, the restenosis rate may be lowered to 5-10%, depending on the size and length of the diseased segments. They therefore reduce the need for a repeated procedure. However, compared with bare metal stents, there may be an increase in the thrombosis rate.
There therefore exists a need for a device for reducing restenosis following PCTA, or any other lumen support procedure using stents, and which overcomes at least some of the disadvantages of prior art systems and methods.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.